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At the end of this lab, students should know...
An alcohol is an organic compound possessing a hydroxyl functional group connected to an alkyl or aryl group (ROH).
Primary aliphatic alcohols are those with one alkyl group connected to the carbon bonded to the OH group. Secondary aliphatic alcohols are those with a hydroxyl group connected to a carbon that has two alkyl groups. Tertiary aliphatic alcohols are those where the hydroxyl group is connected to a carbon that has three alkyl groups. Aromatic alcohols are alcohols that have a hydroxyl group connected to the carbon of a ring structure such as benzene.
The Jones Test is used to distinguish between different aliphatic alcohols. The addition of Jones’ reagent to primary or secondary alcohols causes a color change from red-orange to a dark green precipitate based on the reduction of chromium(VI) to chromium(III). Tertiary aliphatic alcohols do not react.
The Lucas Test uses the reaction rate to distinguish between the three types of aliphatic alcohols. Tertiary alcohols react immediately, forming a secondary phase in the reaction mixture. Secondary alcohols react more slowly, forming layers in solution over the course of several minutes. Primary alcohols do not react unless heat is added, forming a cloudy solution.
The ferric chloride test is used to test for the presence of aromatic compounds. Ferric chloride reacts with the aromatic alcohol to form a purple solution due to the displacement of the chloride anions with the aromatic rings. Ferric chloride will not react with any aliphatic alcohol.
Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA
Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.
|13 Small test tubes|
|1 Test tube rack|
|3 Small vials with caps|
|1 50-mL beaker|
|1 250-mL beaker|
|1 5-mL graduated cylinder|
|1 Glass stirring rod|
|1 Roll of labels or lab tape|
|1 Labeling pen/marker|